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// ContentHandler.java - handle main document content.
// http://www.saxproject.org
// Written by David Megginson
// NO WARRANTY!  This class is in the public domain.
// $Id: ContentHandler.java,v 1.2 2004/11/03 22:44:51 jsuttor Exp $

package org.xml.sax;


/**
 * Receive notification of the logical content of a document.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
 * for further information.
 * </blockquote>
 *
 * <p>This is the main interface that most SAX applications
 * implement: if the application needs to be informed of basic parsing
 * events, it implements this interface and registers an instance with
 * the SAX parser using the {@link org.xml.sax.XMLReader#setContentHandler
 * setContentHandler} method.  The parser uses the instance to report
 * basic document-related events like the start and end of elements
 * and character data.</p>
 *
 * <p>The order of events in this interface is very important, and
 * mirrors the order of information in the document itself.  For
 * example, all of an element's content (character data, processing
 * instructions, and/or subelements) will appear, in order, between
 * the startElement event and the corresponding endElement event.</p>
 *
 * <p>This interface is similar to the now-deprecated SAX 1.0
 * DocumentHandler interface, but it adds support for Namespaces
 * and for reporting skipped entities (in non-validating XML
 * processors).</p>
 *
 * <p>Implementors should note that there is also a
 * <code>ContentHandler</code> class in the <code>java.net</code>
 * package; that means that it's probably a bad idea to do</p>
 *
 * <pre>import java.net.*;
 * import org.xml.sax.*;
 * </pre>
 *
 * <p>In fact, "import ...*" is usually a sign of sloppy programming
 * anyway, so the user should consider this a feature rather than a
 * bug.</p>
 *
 * @author David Megginson
 * @see org.xml.sax.XMLReader
 * @see org.xml.sax.DTDHandler
 * @see org.xml.sax.ErrorHandler
 * @since SAX 2.0
 */
public interface ContentHandler {

  /**
   * Receive an object for locating the origin of SAX document events.
   *
   * <p>SAX parsers are strongly encouraged (though not absolutely
   * required) to supply a locator: if it does so, it must supply
   * the locator to the application by invoking this method before
   * invoking any of the other methods in the ContentHandler
   * interface.</p>
   *
   * <p>The locator allows the application to determine the end
   * position of any document-related event, even if the parser is
   * not reporting an error.  Typically, the application will
   * use this information for reporting its own errors (such as
   * character content that does not match an application's
   * business rules).  The information returned by the locator
   * is probably not sufficient for use with a search engine.</p>
   *
   * <p>Note that the locator will return correct information only
   * during the invocation SAX event callbacks after
   * {@link #startDocument startDocument} returns and before
   * {@link #endDocument endDocument} is called.  The
   * application should not attempt to use it at any other time.</p>
   *
   * @param locator an object that can return the location of any SAX document event
   * @see org.xml.sax.Locator
   */
  public void setDocumentLocator(Locator locator);


  /**
   * Receive notification of the beginning of a document.
   *
   * <p>The SAX parser will invoke this method only once, before any
   * other event callbacks (except for {@link #setDocumentLocator
   * setDocumentLocator}).</p>
   *
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   * @see #endDocument
   */
  public void startDocument()
      throws SAXException;


  /**
   * Receive notification of the end of a document.
   *
   * <p><strong>There is an apparent contradiction between the
   * documentation for this method and the documentation for {@link
   * org.xml.sax.ErrorHandler#fatalError}.  Until this ambiguity is
   * resolved in a future major release, clients should make no
   * assumptions about whether endDocument() will or will not be
   * invoked when the parser has reported a fatalError() or thrown
   * an exception.</strong></p>
   *
   * <p>The SAX parser will invoke this method only once, and it will
   * be the last method invoked during the parse.  The parser shall
   * not invoke this method until it has either abandoned parsing
   * (because of an unrecoverable error) or reached the end of
   * input.</p>
   *
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   * @see #startDocument
   */
  public void endDocument()
      throws SAXException;


  /**
   * Begin the scope of a prefix-URI Namespace mapping.
   *
   * <p>The information from this event is not necessary for
   * normal Namespace processing: the SAX XML reader will
   * automatically replace prefixes for element and attribute
   * names when the <code>http://xml.org/sax/features/namespaces</code>
   * feature is <var>true</var> (the default).</p>
   *
   * <p>There are cases, however, when applications need to
   * use prefixes in character data or in attribute values,
   * where they cannot safely be expanded automatically; the
   * start/endPrefixMapping event supplies the information
   * to the application to expand prefixes in those contexts
   * itself, if necessary.</p>
   *
   * <p>Note that start/endPrefixMapping events are not
   * guaranteed to be properly nested relative to each other:
   * all startPrefixMapping events will occur immediately before the
   * corresponding {@link #startElement startElement} event,
   * and all {@link #endPrefixMapping endPrefixMapping}
   * events will occur immediately after the corresponding
   * {@link #endElement endElement} event,
   * but their order is not otherwise
   * guaranteed.</p>
   *
   * <p>There should never be start/endPrefixMapping events for the
   * "xml" prefix, since it is predeclared and immutable.</p>
   *
   * @param prefix the Namespace prefix being declared. An empty string is used for the default
   * element namespace, which has no prefix.
   * @param uri the Namespace URI the prefix is mapped to
   * @throws org.xml.sax.SAXException the client may throw an exception during processing
   * @see #endPrefixMapping
   * @see #startElement
   */
  public void startPrefixMapping(String prefix, String uri)
      throws SAXException;


  /**
   * End the scope of a prefix-URI mapping.
   *
   * <p>See {@link #startPrefixMapping startPrefixMapping} for
   * details.  These events will always occur immediately after the
   * corresponding {@link #endElement endElement} event, but the order of
   * {@link #endPrefixMapping endPrefixMapping} events is not otherwise
   * guaranteed.</p>
   *
   * @param prefix the prefix that was being mapped. This is the empty string when a default mapping
   * scope ends.
   * @throws org.xml.sax.SAXException the client may throw an exception during processing
   * @see #startPrefixMapping
   * @see #endElement
   */
  public void endPrefixMapping(String prefix)
      throws SAXException;


  /**
   * Receive notification of the beginning of an element.
   *
   * <p>The Parser will invoke this method at the beginning of every
   * element in the XML document; there will be a corresponding
   * {@link #endElement endElement} event for every startElement event
   * (even when the element is empty). All of the element's content will be
   * reported, in order, before the corresponding endElement
   * event.</p>
   *
   * <p>This event allows up to three name components for each
   * element:</p>
   *
   * <ol>
   * <li>the Namespace URI;</li>
   * <li>the local name; and</li>
   * <li>the qualified (prefixed) name.</li>
   * </ol>
   *
   * <p>Any or all of these may be provided, depending on the
   * values of the <var>http://xml.org/sax/features/namespaces</var>
   * and the <var>http://xml.org/sax/features/namespace-prefixes</var>
   * properties:</p>
   *
   * <ul>
   * <li>the Namespace URI and local name are required when
   * the namespaces property is <var>true</var> (the default), and are
   * optional when the namespaces property is <var>false</var> (if one is
   * specified, both must be);</li>
   * <li>the qualified name is required when the namespace-prefixes property
   * is <var>true</var>, and is optional when the namespace-prefixes property
   * is <var>false</var> (the default).</li>
   * </ul>
   *
   * <p>Note that the attribute list provided will contain only
   * attributes with explicit values (specified or defaulted):
   * #IMPLIED attributes will be omitted.  The attribute list
   * will contain attributes used for Namespace declarations
   * (xmlns* attributes) only if the
   * <code>http://xml.org/sax/features/namespace-prefixes</code>
   * property is true (it is false by default, and support for a
   * true value is optional).</p>
   *
   * <p>Like {@link #characters characters()}, attribute values may have
   * characters that need more than one <code>char</code> value.  </p>
   *
   * @param uri the Namespace URI, or the empty string if the element has no Namespace URI or if
   * Namespace processing is not being performed
   * @param localName the local name (without prefix), or the empty string if Namespace processing
   * is not being performed
   * @param qName the qualified name (with prefix), or the empty string if qualified names are not
   * available
   * @param atts the attributes attached to the element.  If there are no attributes, it shall be an
   * empty Attributes object.  The value of this object after startElement returns is undefined
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   * @see #endElement
   * @see org.xml.sax.Attributes
   * @see org.xml.sax.helpers.AttributesImpl
   */
  public void startElement(String uri, String localName,
      String qName, Attributes atts)
      throws SAXException;


  /**
   * Receive notification of the end of an element.
   *
   * <p>The SAX parser will invoke this method at the end of every
   * element in the XML document; there will be a corresponding
   * {@link #startElement startElement} event for every endElement
   * event (even when the element is empty).</p>
   *
   * <p>For information on the names, see startElement.</p>
   *
   * @param uri the Namespace URI, or the empty string if the element has no Namespace URI or if
   * Namespace processing is not being performed
   * @param localName the local name (without prefix), or the empty string if Namespace processing
   * is not being performed
   * @param qName the qualified XML name (with prefix), or the empty string if qualified names are
   * not available
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   */
  public void endElement(String uri, String localName,
      String qName)
      throws SAXException;


  /**
   * Receive notification of character data.
   *
   * <p>The Parser will call this method to report each chunk of
   * character data.  SAX parsers may return all contiguous character
   * data in a single chunk, or they may split it into several
   * chunks; however, all of the characters in any single event
   * must come from the same external entity so that the Locator
   * provides useful information.</p>
   *
   * <p>The application must not attempt to read from the array
   * outside of the specified range.</p>
   *
   * <p>Individual characters may consist of more than one Java
   * <code>char</code> value.  There are two important cases where this
   * happens, because characters can't be represented in just sixteen bits.
   * In one case, characters are represented in a <em>Surrogate Pair</em>,
   * using two special Unicode values. Such characters are in the so-called
   * "Astral Planes", with a code point above U+FFFF.  A second case involves
   * composite characters, such as a base character combining with one or
   * more accent characters. </p>
   *
   * <p> Your code should not assume that algorithms using
   * <code>char</code>-at-a-time idioms will be working in character
   * units; in some cases they will split characters.  This is relevant
   * wherever XML permits arbitrary characters, such as attribute values,
   * processing instruction data, and comments as well as in data reported
   * from this method.  It's also generally relevant whenever Java code
   * manipulates internationalized text; the issue isn't unique to XML.</p>
   *
   * <p>Note that some parsers will report whitespace in element
   * content using the {@link #ignorableWhitespace ignorableWhitespace}
   * method rather than this one (validating parsers <em>must</em>
   * do so).</p>
   *
   * @param ch the characters from the XML document
   * @param start the start position in the array
   * @param length the number of characters to read from the array
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   * @see #ignorableWhitespace
   * @see org.xml.sax.Locator
   */
  public void characters(char ch[], int start, int length)
      throws SAXException;


  /**
   * Receive notification of ignorable whitespace in element content.
   *
   * <p>Validating Parsers must use this method to report each chunk
   * of whitespace in element content (see the W3C XML 1.0
   * recommendation, section 2.10): non-validating parsers may also
   * use this method if they are capable of parsing and using
   * content models.</p>
   *
   * <p>SAX parsers may return all contiguous whitespace in a single
   * chunk, or they may split it into several chunks; however, all of
   * the characters in any single event must come from the same
   * external entity, so that the Locator provides useful
   * information.</p>
   *
   * <p>The application must not attempt to read from the array
   * outside of the specified range.</p>
   *
   * @param ch the characters from the XML document
   * @param start the start position in the array
   * @param length the number of characters to read from the array
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   * @see #characters
   */
  public void ignorableWhitespace(char ch[], int start, int length)
      throws SAXException;


  /**
   * Receive notification of a processing instruction.
   *
   * <p>The Parser will invoke this method once for each processing
   * instruction found: note that processing instructions may occur
   * before or after the main document element.</p>
   *
   * <p>A SAX parser must never report an XML declaration (XML 1.0,
   * section 2.8) or a text declaration (XML 1.0, section 4.3.1)
   * using this method.</p>
   *
   * <p>Like {@link #characters characters()}, processing instruction
   * data may have characters that need more than one <code>char</code>
   * value. </p>
   *
   * @param target the processing instruction target
   * @param data the processing instruction data, or null if none was supplied.  The data does not
   * include any whitespace separating it from the target
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   */
  public void processingInstruction(String target, String data)
      throws SAXException;


  /**
   * Receive notification of a skipped entity.
   * This is not called for entity references within markup constructs
   * such as element start tags or markup declarations.  (The XML
   * recommendation requires reporting skipped external entities.
   * SAX also reports internal entity expansion/non-expansion, except
   * within markup constructs.)
   *
   * <p>The Parser will invoke this method each time the entity is
   * skipped.  Non-validating processors may skip entities if they
   * have not seen the declarations (because, for example, the
   * entity was declared in an external DTD subset).  All processors
   * may skip external entities, depending on the values of the
   * <code>http://xml.org/sax/features/external-general-entities</code>
   * and the
   * <code>http://xml.org/sax/features/external-parameter-entities</code>
   * properties.</p>
   *
   * @param name the name of the skipped entity.  If it is a parameter entity, the name will begin
   * with '%', and if it is the external DTD subset, it will be the string "[dtd]"
   * @throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
   */
  public void skippedEntity(String name)
      throws SAXException;
}

// end of ContentHandler.java
